The present invention relates to a device for sorting products in dependence on a measured parameter, criteria, in particular for sorting small pieces of agricultural products, and products of the food industry or other pieces flowing in sequential masses, and also to a method for operating the device.
In U.S. Pat. 5,388,705 there is described a device for sorting bottles made of plastic, which are classified by a detection station as being contaminated or defective in some other way. The sorting is performed by means of a compressed air-operated ejection mechanism (ram). This solution is based on the condition that the plastic bottles are of a same standard size and are strictly laterally oriented between the detecting station and the ejection mechanism. With this solution four reflected light barriers are employed which are directed level to the serially arriving bottle necks on a conveyer belt, the light barriers are only operating as position indicators and only deliver YES/NO signals. This teaching is not capable of realizing the objects of the present invention.
In DE 195 32 306 A1 there is also described a sorting device for bottles in which a stepper motor drives a cam-disk shaped sorting means which applies a pulse-like impact to the bottles to be sorted. A condition for the operability of the device is the strict alignment of the bottle flow to be sorted, with all the bottles in a same position with respect to a constant narrow space to the sorting device. This solution does not permit a product preserving sorting according to different criteria of a differently composed flow of products as to size and quality.
Known devices that are nearest to the invention are sorting devices from the field of agriculture and food industry. A device is known from DE 27 23 674 A1 in which an ejector plate is provided in a downflow of harvested goods to be sorted, controlled by a preceding detection means and thus being adapted to perform a sorting into two fractions. A similar sorting into two fraction flows is described in DE 27 09 905 A1 which, in particular, separates rocks from harvest goods and in which a finger assembly adjustable in two positions releases, for example, a passageway for a perpendicular falling through of the rocks.
A further improvement is disclosed in an optoelectronic automatic sorting machine as described, for example, in DE 41 27 903. The principle of these selectors is that the products to be sorted are individually and subsequently optoelectronically scanned in a drop chamber by means of image converters which are, for example, in a mutually displaced arrangement of 120xc2x0. Thereby defective products are detected and by means of a suitable calculating program a product detected as defective is separated from the flow of accepted products by an air blast. Such automated sorting mechanisms operate, for example, with potatoes, at a throughput rate of up to 5000 kg/h. As concerns a quality sorting or a sorting out with respect to size of small-sized or sensitive products such as tomatoes, beans, peas, stone fruit, pomaceous fruit, berries, carrots, small carrots, slump-rooted carrots, onions, corn, legume, almonds, nuts, corns of spices, etc. or even, for example, xe2x80x98pommes fritesxe2x80x99, these automated machines, however, are not suited with respect to throughput required or sensitivity of the products.
According to the prior art, the quality sorting out of small-sized products such as, for example, potato chips, pommes frites, lentils or similar small-sized products is carried out in that the products are, if possible, fed upon a conveyer belt at a spaced apart relation, where they are detected by an optoelectronic image converter and, at the end of the conveyer, defective products are separated from the accepted products flow by operation of respectively controlled selection mechanisms.
There are numerous disadvantages involved in such a kind of operation. It is feasible that products superimpose on the conveyer belt so that defective products cannot be detected at all. Products which have been detected as being defective can be subjected to position variations on their way from detection to the output end due to uneven running conveyor belts so that they are moved into another path and, accordingly, are not sorted out. Portions of the products which are turned off-side to the image converter, that is, those surfaces which rest upon the conveyer belt cannot be detected at all. These disadvantages can be obviated by a solution according to DE 196 46 753.5 which also performs only a selection into two fractions, that is, in a go/not go product flow by operation of a compressed air nozzle assembly which is the presently well-known and mildest selection means. Apart from the high expenditures required for the control of the compressed air nozzle assembly, the pulse sequence attainable thereby limits the total throughput that can be obtained for the products to be sorted. Moreover, the energy expenditure required with this ejection solution is very considerable and the acoustic emission can reach up to 90 dB.
It is an object of the present invention to provide a device for sorting any pieces of products in dependence on criteria and also a method for operating the same, which permits a very fast and at least three channel fractionating of a product flow and a simultaneous mild treatment of the products, at a low energy consumption, at a low acoustic emission, and a high wear-resistance, and which, at a change of the products to be sorted from, for example, carrots to onions, screws, plastic parts, is capable of a substantially automatic adaptation to a desired result of the sorting.
When within the scope of the invention there is reference to a sorting in dependence on criteria, then product parameters are to be understood thereby parameters such as volume, speed, profile of parts, center of mass, defective spots, deflection characteristic, angular momentum, or the like.
The very essence of the invention is that products of a sequential product flow pass a first approaching zone, arrive in a second zone, in which a separating element is provided and is rotatable by operation of a stepper motor wherein circumferentially and equally spaced apart fingers are mounted on the separating element and wherein the separating element, depending on a respective control, separates the products into at least three further partial fraction flow zones, accompanied by a real-time image tracking system capable of detecting the entire passage of the products through the three zones. The system feeds individual product information such as volume, speed, profile of parts, center of mass, defective spots, deflection characteristic, angular momentum, or the like into a memory, which information are adapted to be associated and addressable to each individual product. Addresses and address arrays, respectively, of the memory are fixedly related to geometrical coordinates of the zones passed by the products and to the geometric coordinates of the starting position and a congruent position of the separating element, respectively, at a resolution in an order of size of 1 mm/address. An access speed of the memory is at least high enough that, between each image stored by the image tracking system, a plurality of processors are adapted to have to different addresses, and a time-parallel or serial time-multiplex read access to individual product information. The processors by way of suitable programs are adapted to produce control signals which provide the stepper motor, which drives the separating element, with the required displacement-time function. Each respective product thus can be sorted at the right point of time and with the required sense of rotation and acceleration. The stepper motor is provided with a selsyn having a resolution in an order of size of 0.5 degrees, the coordinate signals of which provide the instantaneous values of the controlling stepper motor as to angular position, sense of rotation, speed, and acceleration to the controlling processors.
The operation of the device substantially takes place in the following manner: each piece of product of a sequential product flow, starting from the entry of the same in the first zone, an approaching zone, then a second zone, detectable by a separating element, to a third zone, a partial fraction flow zone, is detected by a real-time image tracking system. Each product from entry into the approaching zone is, in dependence on criteria, detected and continuously stored in the memory. The signals of the memory produced by aid of processors and suitable programs are fed into the stepper motor in such a manner that, when a product to be selected enters the second zone, said stepper motor drives the separating element in a way that a finger of the separating element is accelerated towards the product, it is decelerated for a short time at the moment of contacting the product, and thus applies a specific acceleration to the product. The product is brought into such an end position that, after the product piece selection has been completed, the fingers of the separating element move into a position which, independent of the sense of rotation they have been subjected to, is congruent to their starting position.